Cirrus SR22 Pilot Operating Handbook page 260

Section 7 Cirrus Design
Airplane Description SR22
Airflow Selection
Serials 1602, 1821, 1840, 1863 thru 2437: The airflow selector
regulates the volume of airflow allowed into the cabin distribution
system through mechanical linkage to a butterfly valve in the
distribution manifold. If option installed, the blower fan is turned on
when the selector dial exceeds the full open position.
Serials 2438 and subs: The airflow selector on the system control
panel regulates the volume of airflow allowed into the cabin distribution
system. When the airflow selector is moved past the OFF position an
electro-mechanical linkage actuates a valve in the mixing chamber on
the forward firewall to the full open position. The air is then distributed
by either ram air or by an optional blower fan to the distribution
manifold mounted to the center, aft side of the firewall. The optional
blower fan system includes 0 (ram air), 1 (low fan), 2 (med fan), and 3
(high fan) airflow settings.
Vent Selection
Conditioned air from the distribution manifold can be proportioned and
directed to passengers and/or the windshield by manipulating the
cabin vent selector. The selector is mechanically linked to butterfly
valves at the entrances to the windshield diffuser and the cabin floor
ducting. There is continuous airflow to the panel and armrest eyeball
outlets. Each occupant can control the flow rate from 'off' to maximum
by rotating the nozzle.
When the selector is in the far left position, both butterfly valves are
closed providing maximum airflow to the panel and armrest eyeball
outlets.
Rotating the selector a quarter-turn clockwise opens the cabin floor
butterfly valve allowing airflow to the rear seat foot warmer diffusers
and the front seat outlets mounted to the underside of each kickplate.
Rotating the selector another quarter-turn clockwise opens the
windshield diffuser butterfly valve which permits shared airflow to the
defrosting mechanism and cabin floor outlets.
When the selector is in the far right position, the cabin floor butterfly
valve is closed providing maximum airflow to the windshield diffuser.
7-86 P/N 13772-001
Revision A10